Investigation into the seroprevalence of falcon herpesvirus antibodies in raptors in the UK using virus neutralization tests and different herpesvirus isolates.

Increasing numbers of reports of clinical falcon herpesvirus infection (Falconid herpesvirus-1; FHV-1) have been seen in the UK since 1996. The aim of this epidemiological study was to investigate the seroprevalence of FHV-1 and owl herpesvirus (Strigid herpesvirus-1; StHV-1) infection in the UK, using virus neutralization tests, and to evaluate the prevalence of herpesvirus infection in captive and wild raptor populations. The results, using the English FHV-1 CVL 32/93 isolate, revealed a seroprevalence of 3.97% (10/252). The seroprevalence for StHV-1 was 12.3% (8/65). Analysis of the data by captivity status, age and species revealed that the family Falconidae showed the highest seroprevalence with 6.7% (5/75), while only one of 104 captive Accipitridae was positive for FHV-1 (0.96%). The incidence of FHV-1 neutralizing antibodies in owls was 5.5% (4/73), representing only wild individuals. Eighty-nine serum samples were additionally tested using two other FHV-1 isolates, the German isolate Merlin 1869/92 and the Dutch isolate Peregrine Z100. The seroprevalences of FHV-1 were 28.1% (25/89) and 32.6% (29/89), respectively. All these samples, however, were negative using the CVL 32/92 isolate.